Can some one tell is there any difference between ALTER TABLE executed on ALIAS or TABLE?

You should be able to understand Yourself the difference by rereading the link Sushanth pointed You to
( understanding above all the relation between ALIAS and <TABLE>name ...
what is an ALIAS and its relation to the original object )

no reason for anybody to reread and make a resume of the manuals!

in general to carry on administrative task on DB2 TABLES using the ALIAS is a bad practice!
all the elucubrations and requirements from a design point are carried on on the <base> object;
ALIASes are generally implementd much later in the process and most often because of needs external to the application for which the <table> was designed

Well My objective was not to get bookish answer & theoretical differences.

saying that
siddhartha Bhattacharya is wasting everybody' s time with his stubborness and stupid remarks
is the same thing as saying that
sid-aec is wasting everybody' s time with his stubborness and stupid remarks

once it is clear that sid_aec is an ALIAS for siddhartha Bhattacharya
any other comment is superfluous

well... when You ask on a forum You should be able to accept the answers You are given without criticizing them
if You cannot do that and Your objective is to get only the answers You like,
hire a paid consultant who will , for an appropriate fee (*), happily satisfy Your desires
(*) be prepared to pay for this kind of consultancies four to five times the normal fee!